Relative clauses

NON-DEFINING CLAUSES

EXAMPLES

• He gave me the letter, which was in a blue envelope. (non-defining clause: There was only one letter, it happened to be blue. You must use which)
• He gave me the letter which/that was in a blue envelope. (defining clause: There were several letters of different colors and he gave me the blue one. Which may be replaced by that. The commas are removed.)
• He gave me the letter, which I read immediately. (non-defining clause: There was only one letter. which is the object of read, but it still must be included in the sentence.)
• Stratford-on-Avon, which many people have written about, is Shakespeare's birthplace. (Any preposition that appears is normally placed at the end of the clause.)
• Stratford-on-Avon, about which many people have written, is Shakespeare's birthplace. (In formal written English, you can also put the preposition before the pronoun.)

RELATIVE PRONOUNS

The following relative pronouns are used in non-defining relative clauses. These relative pronouns appear at the start of the non-defining relative clause and refer to a noun that appears earlier in the sentence.

	Person	Thing	Place
Subject	who	which
Object	who/whom	which	where
Possessive	whose

DIFFERENCES WITH DEFINING RELATIVE CLAUSES

In defining relative clauses, the pronouns who, whom, and which are often replaced by that in spoken English.

In non-defining relative clauses, you cannot replace other pronouns with that.

You also cannot leave out the relative pronoun in non-defining relative clauses, in the way you sometimes can in defining relative clauses. The pronoun is required, even when it is the object of the verb in the relative clause. 

Finally, non-defining relative clauses are always separated from the rest of the sentence by commas, unlike defining relative clauses, which have no punctuation.

USING "WHICH" TO REFER TO ANOTHER CLAUSE

The relative pronoun which at the beginning of a non-defining relative clause can refer to all the information contained in the previous part of the sentence, rather than to just one word.

EXAMPLES

• Chris did really well in his exams, which is quite a surprise.
• My friends were all hiding in my apartment, which isn't what I'd expected.
• She's studying to become a doctor, which is difficult.

INTRODUCTORY EXPRESSIONS IN NON-DEFINING CLAUSES

Non-defining clauses can be introduced by expressions like all of or many of followed by the relative pronoun.

	Person	Thing
all of, any of, some of, a few of, both of, each of, either of, half of, many of, most of, much of, none of, one of, two of, etc.	whom	which

EXAMPLES

• There were a lot of people at the party, many of whom I had known for years.
• There are 14 girls in my class, a few of whom are my friends.
• He was carrying his belongings, many of which were broken.
• He had thousands of books, most of which he had read.
• He picked up a handful of stones, one of which was sharp.